Just came across this thread. I notice you didn't say when in June you plan to go. Sites in Yosemite (especially ones large enough to handle your rig) are minimal, and will sell out w/in seconds of when the booking window opens...especially for June. Arrival dates for up to June 14 are already booked.
I have only been on the road from 395 to Benton on a bicycle, and I remember a pretty good grade between Benton and Black lake. And of course heading up Tioga Pass into the park is a very long/steep grade as well (have done both ways on the bike as well when camping at Tuolumne Meadows).
As someone else mentioned, 395 from to Reno is a great road, and if you do come up from Bishop you could do the June Lakes loop, nice and scenic (especially on a bicycle!)
Obviously Ca. is going through a drought, and if it continues snow won't be an issue, but as can see from this chart, in 2011 Tioga pass didn't even open until June 18th; Tioga and Glacier Point Roads Opening & Closing Dates - Yosemite National Park (U.S. National Park Service)
We generally stop at Whoa Nellie Deli when in the area. Nice little break before heading up Tioga Pass: http://www.tripadvisor.com/Restauran...alifornia.html
And has been mentioned, gas prices in Lee Vining are over a dollar higher per gallon than in Reno, and about 80 cents higher than in Bishop.
I worked in Yosemite for 2 summers and winter back in '64-'65, and have been camping there my whole life. Now we take the grand-kids up every spring break.